/*
 * $Header:
 * /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons
 * //httpclient/src/java/org/apache/commons/httpclient/ChunkedInputStream.java,v
 * 1.24 2004/10/10 15:18:55 olegk Exp $ $Revision: 480424 $ $Date: 2006-11-29
 * 06:56:49 +0100 (Wed, 29 Nov 2006) $
 *
 * ====================================================================
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many individuals on
 * behalf of the Apache Software Foundation. For more information on the Apache
 * Software Foundation, please see <http://www.apache.org/>.
 */

package com.microsoft.tfs.core.httpclient;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.microsoft.tfs.core.httpclient.util.EncodingUtil;
import com.microsoft.tfs.core.httpclient.util.ExceptionUtil;

/**
 * <p>
 * Transparently coalesces chunks of a HTTP stream that uses Transfer-Encoding
 * chunked.
 * </p>
 *
 * <p>
 * Note that this class NEVER closes the underlying stream, even when close gets
 * called. Instead, it will read until the "end" of its chunking on close, which
 * allows for the seamless invocation of subsequent HTTP 1.1 calls, while not
 * requiring the client to remember to read the entire contents of the response.
 * </p>
 *
 * @author Ortwin Glueck
 * @author Sean C. Sullivan
 * @author Martin Elwin
 * @author Eric Johnson
 * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
 * @author Michael Becke
 * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
 *
 * @since 2.0
 *
 */
public class ChunkedInputStream extends InputStream {
    /** The inputstream that we're wrapping */
    private final InputStream in;

    /** The chunk size */
    private int chunkSize;

    /** The current position within the current chunk */
    private int pos;

    /** True if we'are at the beginning of stream */
    private boolean bof = true;

    /** True if we've reached the end of stream */
    private boolean eof = false;

    /** True if this stream is closed */
    private boolean closed = false;

    /** The method that this stream came from */
    private HttpMethod method = null;

    /** Log object for this class. */
    private static final Log LOG = LogFactory.getLog(ChunkedInputStream.class);

    /**
     * ChunkedInputStream constructor that associates the chunked input stream
     * with a {@link HttpMethod HTTP method}. Usually it should be the same
     * {@link HttpMethod HTTP method} the chunked input stream originates from.
     * If chunked input stream contains any footers (trailing headers), they
     * will be added to the associated {@link HttpMethod HTTP method}.
     *
     * @param in
     *        the raw input stream
     * @param method
     *        the HTTP method to associate this input stream with. Can be
     *        <tt>null</tt>.
     *
     * @throws IOException
     *         If an IO error occurs
     */
    public ChunkedInputStream(final InputStream in, final HttpMethod method) throws IOException {

        if (in == null) {
            throw new IllegalArgumentException("InputStream parameter may not be null");
        }
        this.in = in;
        this.method = method;
        pos = 0;
    }

    /**
     * ChunkedInputStream constructor
     *
     * @param in
     *        the raw input stream
     *
     * @throws IOException
     *         If an IO error occurs
     */
    public ChunkedInputStream(final InputStream in) throws IOException {
        this(in, null);
    }

    /**
     * <p>
     * Returns all the data in a chunked stream in coalesced form. A chunk is
     * followed by a CRLF. The method returns -1 as soon as a chunksize of 0 is
     * detected.
     * </p>
     *
     * <p>
     * Trailer headers are read automcatically at the end of the stream and can
     * be obtained with the getResponseFooters() method.
     * </p>
     *
     * @return -1 of the end of the stream has been reached or the next data
     *         byte
     * @throws IOException
     *         If an IO problem occurs
     *
     * @see HttpMethod#getResponseFooters()
     */
    @Override
    public int read() throws IOException {

        if (closed) {
            throw new IOException("Attempted read from closed stream.");
        }
        if (eof) {
            return -1;
        }
        if (pos >= chunkSize) {
            nextChunk();
            if (eof) {
                return -1;
            }
        }
        pos++;
        return in.read();
    }

    /**
     * Read some bytes from the stream.
     *
     * @param b
     *        The byte array that will hold the contents from the stream.
     * @param off
     *        The offset into the byte array at which bytes will start to be
     *        placed.
     * @param len
     *        the maximum number of bytes that can be returned.
     * @return The number of bytes returned or -1 if the end of stream has been
     *         reached.
     * @see java.io.InputStream#read(byte[], int, int)
     * @throws IOException
     *         if an IO problem occurs.
     */
    @Override
    public int read(final byte[] b, final int off, int len) throws IOException {

        if (closed) {
            throw new IOException("Attempted read from closed stream.");
        }

        if (eof) {
            return -1;
        }
        if (pos >= chunkSize) {
            nextChunk();
            if (eof) {
                return -1;
            }
        }
        len = Math.min(len, chunkSize - pos);
        final int count = in.read(b, off, len);
        pos += count;
        return count;
    }

    /**
     * Read some bytes from the stream.
     *
     * @param b
     *        The byte array that will hold the contents from the stream.
     * @return The number of bytes returned or -1 if the end of stream has been
     *         reached.
     * @see java.io.InputStream#read(byte[])
     * @throws IOException
     *         if an IO problem occurs.
     */
    @Override
    public int read(final byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    /**
     * Read the CRLF terminator.
     *
     * @throws IOException
     *         If an IO error occurs.
     */
    private void readCRLF() throws IOException {
        final int cr = in.read();
        final int lf = in.read();
        if ((cr != '\r') || (lf != '\n')) {
            throw new IOException("CRLF expected at end of chunk: " + cr + "/" + lf);
        }
    }

    /**
     * Read the next chunk.
     *
     * @throws IOException
     *         If an IO error occurs.
     */
    private void nextChunk() throws IOException {
        if (!bof) {
            readCRLF();
        }
        chunkSize = getChunkSizeFromInputStream(in);
        bof = false;
        pos = 0;
        if (chunkSize == 0) {
            eof = true;
            parseTrailerHeaders();
        }
    }

    /**
     * Expects the stream to start with a chunksize in hex with optional
     * comments after a semicolon. The line must end with a CRLF: "a3; some
     * comment\r\n" Positions the stream at the start of the next line.
     *
     * @param in
     *        The new input stream.
     * @param required
     *        <tt>true<tt/> if a valid chunk must be present, <tt>false
     *        <tt/> otherwise.
     *
     * @return the chunk size as integer
     *
     * @throws IOException
     *         when the chunk size could not be parsed
     */
    private static int getChunkSizeFromInputStream(final InputStream in) throws IOException {

        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
        // States: 0=normal, 1=\r was scanned, 2=inside quoted string, -1=end
        int state = 0;
        while (state != -1) {
            int b = in.read();
            if (b == -1) {
                throw new IOException("chunked stream ended unexpectedly");
            }
            switch (state) {
                case 0:
                    switch (b) {
                        case '\r':
                            state = 1;
                            break;
                        case '\"':
                            state = 2;
                            /* fall through */
                        default:
                            baos.write(b);
                    }
                    break;

                case 1:
                    if (b == '\n') {
                        state = -1;
                    } else {
                        // this was not CRLF
                        throw new IOException(
                            "Protocol violation: Unexpected" + " single newline character in chunk size");
                    }
                    break;

                case 2:
                    switch (b) {
                        case '\\':
                            b = in.read();
                            baos.write(b);
                            break;
                        case '\"':
                            state = 0;
                            /* fall through */
                        default:
                            baos.write(b);
                    }
                    break;
                default:
                    throw new RuntimeException("assertion failed");
            }
        }

        // parse data
        String dataString = EncodingUtil.getAsciiString(baos.toByteArray());
        final int separator = dataString.indexOf(';');
        dataString = (separator > 0) ? dataString.substring(0, separator).trim() : dataString.trim();

        int result;
        try {
            result = Integer.parseInt(dataString.trim(), 16);
        } catch (final NumberFormatException e) {
            throw new IOException("Bad chunk size: " + dataString);
        }
        return result;
    }

    /**
     * Reads and stores the Trailer headers.
     *
     * @throws IOException
     *         If an IO problem occurs
     */
    private void parseTrailerHeaders() throws IOException {
        Header[] footers = null;
        try {
            String charset = "US-ASCII";
            if (method != null) {
                charset = method.getParams().getHttpElementCharset();
            }
            footers = HttpParser.parseHeaders(in, charset);
        } catch (final HttpException e) {
            LOG.error("Error parsing trailer headers", e);
            final IOException ioe = new IOException(e.getMessage());
            ExceptionUtil.initCause(ioe, e);
            throw ioe;
        }
        if (method != null) {
            for (int i = 0; i < footers.length; i++) {
                method.addResponseFooter(footers[i]);
            }
        }
    }

    /**
     * Upon close, this reads the remainder of the chunked message, leaving the
     * underlying socket at a position to start reading the next response
     * without scanning.
     *
     * @throws IOException
     *         If an IO problem occurs.
     */
    @Override
    public void close() throws IOException {
        if (!closed) {
            try {
                if (!eof) {
                    exhaustInputStream(this);
                }
            } finally {
                eof = true;
                closed = true;
            }
        }
    }

    /**
     * Exhaust an input stream, reading until EOF has been encountered.
     *
     * <p>
     * Note that this function is intended as a non-public utility. This is a
     * little weird, but it seemed silly to make a utility class for this one
     * function, so instead it is just static and shared that way.
     * </p>
     *
     * @param inStream
     *        The {@link InputStream} to exhaust.
     * @throws IOException
     *         If an IO problem occurs
     */
    static void exhaustInputStream(final InputStream inStream) throws IOException {
        // read and discard the remainder of the message
        final byte buffer[] = new byte[1024];
        while (inStream.read(buffer) >= 0) {
            ;
        }
    }
}
